Better CSS handling

[baransu]

I'm creating this issue because since we ejected create-react-app we can tweak our CSS imports a little.

Two options I'm thinking of are:

• CSS modules - allow us to keep CSS restricted to given component which is great
• SASS - variables, less code

I'm leaning towards CSS modules.

[baransu]

Another options is styled-components. It's great for creating components package for consistent plugin look in the future.